Various electro-optical systems have been developed for reading optical indicia, such as barcodes. A barcode is a coded pattern of graphical indicia comprised of a matrix or series of bars and spaces of varying widths, the bars and spaces having differing light reflecting characteristics.
Systems that read barcodes called barcode readers electro-optically transform the graphic indicia into electrical signals and then decode the electric signals into alphanumerical characters that are intended to be descriptive of the article or some characteristic thereof. There are different types of barcode readers or scanners each including different set of components and employing different methods, to read a barcode. The types include such as, but not limited to, pen type readers, laser scanners, CCD readers, and 2D imaging scanners.
Pen type readers consist of a light source and a photodiode that are placed next to each other in the tip of a pen or wand. In order to read a barcode present on a label on a target object, the tip of the pen is moved or swiped across the label in a steady motion. The photodiode measures the intensity of the light reflected back from the light source and generates a waveform that is used to measure the widths of the bars and spaces in the barcode.
Laser scanners work the same way as pen type readers except that they use a laser beam as the light source and typically employ either a reciprocating mirror or a rotating prism to scan the laser beam back and forth across the target object.
CCD readers (also referred to as LED scanner) use an array of hundreds of tiny light sensors lined up in a row in the head of the reader. Each sensor measures the intensity of the light immediately in front of it. The important difference between a CCD reader and a pen or laser scanner is that the CCD reader is measuring emitted ambient light from the barcode whereas pen or laser scanners are measuring reflected light of a specific frequency originating from the scanner itself.
2D imaging scanners use a small video camera to capture an image of the barcode. The reader then uses sophisticated digital image processing techniques to decode the barcode.
In all the above cases, the ability of a scanner to successfully read and decode a target object is directly dependent upon the ability to move the scanner to a suitable position whereby a satisfactorily clear image of the target object is obtained. In order to obtain a clear image of the target object, the scanner has to be properly directed or aimed towards the target object. In general all the present day scanners have an aiming pattern generator for generating a visible aiming pattern. The visible aiming pattern can include such as, but not limited to, a laser dot or a laser line that enables an operator to aim the scanner at the target object and thereby read the target object.
However, at long distances or in high ambient light the aiming pattern generator might fail to accurately aim the particular target object. In cases of high ambient light such as sunlight, the laser aiming dot is not visible. On the other hand, in low light conditions such as scanning in a warehouse, the laser aiming dot may not be easily visible at large distances. Also, aiming at large distances could also be difficult in cases where there is no reflective background to see the current position of the laser dot to help guide the operator towards the barcode. In such conditions, one way of improving the visibility of the laser aiming dot can be achieved by increasing the laser power. However, this method is limited due to laser safety regulations. Another way to improve visibility is by making the operator wear colored glasses such as red glasses for a red laser to filter out ambient light, but this has the inconvenience of having to manage a supply of glasses.
Accordingly, there is a need for an alternate method to aim the barcode scanner at the desired target object.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.